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Circular No 156. 


tinted States Department of Agriculture, 

L. O. HOWARD, Entomologist and Clue! oi Bureau. 


f 1 S\ 


i\ ntoDi i tion. 

the principal causes of the deterio- 
ration and destruction of timb ! in mines. The injury is 
ted both before and in - nl in the mine. 
This circular is based on special investigations in cooperation with 
mining companies. It is intended to give preliminary information 
on the principal types of insect injury ind to show bow a large per- 
f injury can be prevented. 
In recenl publications of this bun rmation is given 
on methods for the prevention of injury by insects t< products, 
including mine props S ral of these methods have been adapted 
to tlic need of preventing injury i<> this special class of product, and 
are included in the present circular. 

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Both »ft and hardwood timber, which has been Mid for mine 
props, and onbarked props thai have been cut and left lying stacked 
in the woods or in the yard at the entrance to the mine, are liable to 
infestation with the grubs or larvae of wood-boring insects. These 
grubs, which hatch from eggs deposited by winged insects attracted 
by the odor of the fresh-cut timber, eontTm**i-la_\vorl\ in the props 

1 Insed D«>pro.tnt!i>n< in North American For 
Dept I Insect Injuries to Forest Products. ( 

Apr .19 

•-Cir 166— 12 

V. linrai, 



after they have been transported from the woods and placed in the 
mine. The grubs of most injurious wood-boring insects can not be- 
come established in the timber unless the bark is on, because the bark 
serves as a protective covering under which the eggs can be deposited 
and affords proper moisture conditions for the development of the 
young grubs, many of which feed on the inner bark before entering 
the wood. The principal injuries to mine props by wood-boring 
insects are those caused by roundheaded and flatheaded borers, timber 
worms, and ambrosia beetles. 

Injury to timbers by roundheaded and flatheaded borers and tim- 
ber worms consists in burrows in the wood made by grubs, which 
hatch from eggs laid under the bark by winged beetles. These bur- 
rows, often of large size, not only decrease the length of service of 
the timbers, but also their structural strength. Running both trans- 
versely and longitudinally through the wood, these holes, even if the 
insects have discontinued their work, afford entrance to moisture and 
wood-destroying fungi ; the decay is thus enabled more rapidly and 
completely to penetrate the heartwood. 

Injury by ambrosia beetles consists of pinhole and bluing defects 
in the wood. The pinhole defects also contribute to more rapid 

There is, therefore, a complicated interrelation between these wood- 
boring insects and wood-destroying fungi in the deterioration of mine 


In the Southern States the principal injury to props and other 
timbers in slope or incline mines is caused by small, white, soft- 
bodied insects known as " wood lice," white ants, or termites. These 
destructive insects work in moist or decaying wood. Timbers placed 
on the heavily timbered slope or incline, extending from 250 to 300 
feet from the exterior into the mine, are attacked by termites, as 
are those used in "headings" near the surface of the ground. Indi- 
viduals of the winged form enter the mine and establish colonie- at 
the base of the props. The moist condition of the prop at the base, 
where the wood is in contact with the ground and where there is 
usually incipient decay, offers especially favorable conditions for 
injury by this class of insects. 

The presence of these insects is not easily detected. Their work 
is hidden beneath an outer shell of wood, often very thin, but always 
left intact; therefore an ordinary inspection of the exterior of the 
props will not reveal the presence of the insects or their destructive 
work. The entire interior may be completely honeycombed while 
there is nothing on the exterior to indicate the injury. Sometimes 
an earthy matter — partially digested wood mixed with earth — is em- 

[Clr. 156] 

!.\-i . i DAM \'.i I" MINI PB0P8. •'{ 

ployed in cover over such parts of their work as would otherwise be 
exposed to 1 1 1«- light, which thej carefully ;i\<>i,|. 

Ii is well known thai when once these insects have gained an 
entrance to the outer moist <>r decayed layers of wood they can con 
limn' their destructive \\'>rk into the 90imd heartwood; on ill 
count it is \«'i\ important t" prevent them from becoming established. 


I'., simply adapting methods <>f handling the timbers, before 
placement, t<> well-known facts in tin- life history of the insects .1 
large percentage of injur] can be prevented. It' a sufficient quantity 
of props be cul far enough ahead of the time when needed, and stored 
either in the \ ait I at the mine or in ;i general storage yard most 
siblc to the largest number of mines, they can Ik- properly 
handled to prevent insect injury and ;i reserve supply established. 
The logs should be barked in the woods wnlun ;i few days after 
felling the trees. A.fter cutting ini<> props they should be trans- 
ported to the place of storage and piled in loose stacks in such a 
manner as t<> facilitate rapid drying, guarding against excessive 
checking. After a reserve supply has l"' 1 !! established it will n<> 
longer be necessary to cut mine timber during the warmer months 
when tlif insects which deposit eggs in the bark or wood are flying. 
llif periods during which these insects are flying vary with the 
locality and the species of insect, l>ut. in general, in the region north 
tit" the Gulf States the period of activity is from April to the middle 
>t' October. In all cases where timbers are to be left stacked, either 
in the woods or yard, the bark must be removed before the end of 
M h to a\ « » i « 1 attack by insects. 

l'»\ barking and seasoning mine timbers, insect injury before place- 
ment will not only be prevented, but injury by termites after place- 
ment will also be delayed or under some conditions even prevented 
and the length of life of the timbers prolonged. 

Therefore the timber should always be barked except in rare in- 
stances where it is to be used in workings of a very temporary char- 
acter. It' unbarked round or split props are to be used in temporary 
workings where it would not be practicable to remove the I >ark. the 
should be cut during the fall and early winter. A- soon as 
possible after cutting, prop- should be stacked in "open-crib" pile3 
in a place where they will dry most rapidly, without excessive check- 
ing, preferably after they have been transported from the woods, be- 
cause if the inner bark i> dried <>ut before the insects begin to fly in 
the spring the more destructive insects will n<>i attack them. >plit 
prop- should be piled with the hark side up so thai the inner bark 
will dry. I., gs or prop- should not be left lying on the ground. I n- 

[Olr. 166] 




3 1262 09216 6106 

harked props, especially props cut from insect-killed, fire-killed, or 
other dead standing timber, .should be thoroughly inspected before 
they arc placed in the mine and all props showing serious damage l>v 
insects discarded. The presence of wood-boring insects can be de- 
tected by sawdust-like boring dust thai is expelled from their bur- 
rows and lodges in crevice.- in the hark. 


As previously stated, the seasoning that prevents injury before 
placement will delay and under some conditions even prevent injury 
to mine timbers hv termites after placement, since moisture or incip- 
ient decay is necessary for destructive work. In consequence, 
soiling is recommended where it is impracticable to treat timbers 
with chemical preservatives. 

Methods of superficially treating props by brushing the exterior 
with various chemical preservatives will be temporarily effective in 
keeping out termites, if the work is thoroughly done and both ends 
are also treated. Where the basal area is left untreated, termite- 
will enter the prop through the untreated portion. It will readily 
be seen that neither brushing nor spraying the exterior of the prop 
after placement in the mine, as is sometimes practiced, is effective 
in keeping out termites, since the end that sets in the ground could 
not be treated, and it is usually here that termite.- attack the props. 

Before treating timber with chemical preservatives, especially where 
the brush method is used, it is essential that the timber be thoroughly 
seasoned, otherwise penetration will he retarded. 

Impregnating props intended for permanent service with creosote 
by some standard process (either by the "open-tank" or by the 
cylinder-pre»ure processes) will keep out termites and other wood- 
boring insects and preserve the prop- for a much longer period than 
they would last untreated. 

Publications of the Forest Service should he consulted for infor- 
mation on general methods of treating timbers with preservatives 
and the relative efficiency of various methods and chemicals. 1 


James "Wilson, 
Secrt tary of Agriculture. 
Washington, D. C, April JO. 1912. 

1 See especially Bulletin 107 of the Forest Service, D. S. Department of Agriculture, 
" The V reservation of Mine Timbers." 
U'ir. 156] 

ADDITIONAL COPIES of this publication 
■£*- may be procured from the Superintend- 
ent of Documents, Government Printing 
Office, Washington. D. C, at 5 cents per copy.